Spark-gap assembly for lightning arresters



Aug. 11, 1959 w. H. NASH 2,899,602

SPARK-GAP ASSEMBLY FOR LIGHTNING ARRESTERS Filed Dec. 10, 1956 IN V EN TOR. ZVZ'ZZiam H. My:

United States Patent SPARK-GAP ASSEMBLY FOR LIGHTNING ARRESTERS William H. Nash, South Milwaukee,

Wis., assignor to McGraw-Edison Company,

The present invention relates to lightning arresters, and particularly pertains to an improved spark-gap assembly therefor.

It is an object of the present invention to provide an improved spark-gap assembly for valve type lightning arresters, wherein said assembly provides a relatively greater surface creepage distance for a predetermined number of gap electrodes, without adding to the relative overall length of said assembly.

Another object of the present invention is to provide a spark-gap assembly including gap electrodes and electrode spacers of either or both resistor and capacitance types, wherein said spacers preferably take the form of annular ringlike members concentrically arranged to concurrently provide alternate predetermined spark gaps between respective electrode members.

A further object of the present invention is to provide an improved spark-gap assembly, in its preferred embodiment, having annular spacer members in its preferred construction wherein the cross-sectional area of each of concentrically arranged spacers is substantially identical relative to a horizontal plane taken through the respective spacer members, thereby providing spacers of substantially identical resistance or capacitance respectively.

It is still another object of the present invention to provide an improved spark gap assembly including stacked electrode members disposed concentrically of a high dielectric rod-like member, and wherein said electrodes are spaced apart by alternately arranged annular spacer members of either capacitance or resistance material, or alternately arranged, if so desired.

The spark-gap assembly of the present invention takes a form which is readily adaptable for use in conventional valve-type lightning arrester constructions, and may be disposed at either or both ends of an arrester with respect to the valve material.

The present invention will be more clearly explained with attention being given to the following specific description, aided by the drawing, in which:

Fig. 1 is a top plan view of a spark-gap assembly according to the present invention.

Fig. 2 is a vertical section of a fragmentary portion of a spark-gap assembly according to the present invention, which section is taken on lines 2-2 of Fig. 1.

Although the spark-gap assembly of the present invention may be accommodated to a lightning arrester of any of the conventional types, or to other suitable equipment, it will be apparent that it may be substituted for the spark-gap assembly of a valve-type arrester, of the general type disclosed in Fig. 1 of my copending applica tion for Lightning Arrester, Serial No. 597,627, filed July 13, 1956, and assigned to the same assignee as is the present invention.

With reference to the drawing, the spark-gap assembly comprises an are or spark-gap pile including a plurality of spaced, plate-like conducting electrodes, indicated generally by the reference numeral 1, and each electrode is substantially identical to each of the others. Each electrode is preferably formed from sheet material in a general concavo-convex configuration and each is formed so that when the electrodes are properly assembled, the respective base surfaces and outer marginal flanged surfaces will provide alternate arc gaps 2 and 3, respectively, between respective adjacent electrodes.

The marginal flanged surface of electrodes 1 are provided with circumferentially spaced embossments 4, preferably three in number and equally spaced. The embossments provide a stable support means for the spaced electrodes, as will hereinafter be described. As illustrated in Fig. 2, each of the various electrodes are arranged in alternate reverse relationship about a rod-like member 5, preferably positioned in a center opening 6 in each electrode. It is further to be noted, that the opening 6 is provided with circumferentially spaced radially inwardly projecting prongs 7 to give a better ionization level, than would be if only a circular hole were punched to receive the rod. The rod-like member 5 is of insulating material of preferably relatively high dielectric constant, such as steatite having a dielectric constant of approximately 4 or 5.

Each of the plate-like electrodes 1 the rod-like member 5 be adjacent or opposite are positioned on so that the face of one disk will that of the adjacent disk. Thus, the embossments 4 will project towards one another from respective electrodes, as illustrated in Fig. 2.

It is also to be noted that the electrodes are formed to provide an inwardly protruding base portion 8 having an annular bead or embossment defining spark gap 2 with the like base portion of an adjacent electrode memher.

The present construction also permits the use of spacer members having particular desirable characteristics. That is, the embossments 4 of the opposed electrodes are mainrained in dimensional relationship by means of a spacer member 10, preferably annular in shape, concentric with the axis of the rod-like member 5, and circumjacent to the base portion 8 of respective electrodes. Thus, the embossments 4 of which three equally spaced portions are preferred, provide a 3-point contact with both the opposed electrodes of respective sets to make a physically stable gap 2 between the electrodes, in that the parts will not tend to rock due to slight irregularities in relative flat surfaces. As heretofore mentioned, the spacer member 10 may be in the form of a grading resistance of about 1 megolnn per resistor, or may be of a ceramic composition having a predetermined dielectric constant to provide a desired capacitance characteristic. Thus, an overall capacitance or resistance grading may be provided thereby.

An additional intermediate spacer member 11, preferably of annular shape, is also provided to establish a predetermined gap 3 between adjacent electrodes 1. Here, the base portion 8 of each electrode rests immediately adjacent the spacer member 11, as shown in Fig. 2. As stated above, the spacer member 11 may be of either the resistance or capacitance type, as desired. The spacer member 11 is also preferably concentrically arranged relative to the axis of the rod-like memher 5 and telescopically related to an adjacent juxtaposed spacer member 10.

It will be apparent thatthe present arrangement of spacer members provides added stability over the cylindrical spacers disposed between the electrodes of the gap assembly of my above-mentioned copending application and other prior art embodiments of similar nature. The present spacers are also relatively easy to assemble by comparison with separated spacers.

It is to be noted that the term annular, as applied to spacer members 10 and 11 in the description and appended claims, is to be considered in its broadest sense to include a closed ring-like member of any internal or external configuration, such as a polygon, capable of relative concentric zirrangemenhfalthough, for simplicity in manufacture, and design, a circular member is preferred. It is also to benoted that the particular elec: trode structure may be adapted for use with other spacer members if so desired. However, the combinationof elements disclosed in the drawing is preferred.

Another feature of the present invention, is brought forth in a preferred embodiment, wherein the cross-sectional area, taken on a horizontal plane (for instance, as viewed in the plan view. of Fig. 1) would be established at substantially the same value for both of the respective spacer members Iii-and 11. 'Thus, either the resistance value or the capacitance value, as desired, of the two physically different. spacers, with reference to the respective outer diameter and the inner diameter, would be the same. Obviously, this becomes'important in the establishment of a uniformly graded gap structure.

it will be apparent that the gap assembly of the present invention provides a ruggedstructure which will not be easily damaged even by rough handlingduring assembly or during installation and use of the finished arrester. The assembly also provides a structure which is easily assembled, which tends to reduce its manufacturing costs.

Furthermore, since the series. gaps are relatively isolated from one another, the flashover characteristic (as opposed to sparkover) is greatly improved. This tends to improve the follow current clearing ability of'the present gap assembly.

I claim:

1. A spark gap assembly comprising a pile of annular spaced apart electrodemembers each having a general ccncavo-convex configurationdefining anannular base portion and a concentric radially spaced marginal flanged portion and being arranged in said pile to face alternately in opposed directions, said base portion and said flanged portion respectively jointly defining alternate spark gap surfaces with like surfaces of said. opposed electrode members, and annular concentric insulating members interposed between a djacentelectrode, members to provide a means for maintaining predetermined spark gap dimensions between the said respective opposed portions, said insulating members comprising a first annular member disposed between said base portions to maintain the spark gap dimension between the spark gap surfaces of .said flanged portion and a second annular member concentrically circumjacent to said first insulatingrnember and to said base portion spark gap surface and disposed between said respective flanged portions to maintain the spark gap dimension between respective opposed base portion spark gap surfaces,

2. A spark gap assembly asset forth in claim 1 wherein the base portion is formed with a pluralityiof radially inwardly projecting ionization prongs.

3. A spark gapassembly comprising a pile of spaced apart electrode members each having a general concavoconvex configuration defining an annular base portion and a concentric radially spaced marginal flanged portion and being arranged in said pile to face alternately in opposed direction, said base portion and said flanged portion re spectively jointly defining alternate spark gap surfaces with like surfaces of said opposed electrode members, and insulating members interposed between adjacent electrode members to provide a means for maintaining predetermined spark gap dimensions between the said respective opposed portions, said opposed flanged portions each including equally circumferentially spaced depressed embossments in abutting engagement with the respective insulating mem er I disposed therebetween.

4. A spark gap assembly comprising a pile of spaced apart electrode members each having a general concavoconvex configuration defining an annular base portion and a radially spaced concentric marginal flanged portion and being arranged in said pile to face alternately in opposed direction, said base portion and said flanged portion respectively jointly defining alternate spark-gap surfaces with like surfacesof said opposed electrode members, and annular insulating members interposed between adjacent electrode members to provide a means for maintaining predetermined spark gap dimensions between the said respec tive opposed portions, and a rod-like insulating member disposed in each of said centrally located apertures, said insulating members comprising a first annular member concentric relative to said rod-like member and disposed between said opposed base portions and a second annular insulating member circumjacent to and concentric with said first annular member, said opposed flanged portions each including three equally circumferentially space d'depressed embossments in abutting engagement with said second annular insulating member. 7

5. A spark gap assembly as set forth in claim 4 wherein the base portion of the electrode members are formed with a plura ity of inwardly projecting ionization prongs for cooperation .with. the rod like insulating member.

6. Aspark. gap assembly comprising a pile of spaced apart electrodelmembers each having a general concavoconvex configuration. defining a base portion and a radially spaced marginal'flanged portion and being'arranged in said pileto face alternately in opposed direction, said base portion and said flanged portion respectively jointly defining alternate spark. gap .surfaces with like surfaces of said opposed electrode .members,.and insulating members inter.

posed between adjacent electrode members to provide a meansfor maintainingpredetermined spark gap dimens1onsbetween the saidmrespectiveopposed portions, said insulating members consisting of an inner annular member disposed between said base portions and an outer annular member circumjacentto.andLCOncentric with said inner memberand disposed between said respective flanged portions, each of said insulating members defining a substantially egualcross-sectional area taken in a plane substan tially normal to their respective concentric axis.

References Cited in the file of this patent. UNITED STATES PATENTS 1,213,844 Creighton Ian. 30, 1917 2,324,108 Pyk .Tulyi13, 1943 2,623,197 Kalb Dec. 23, 1952 

